I. Field of the Invention
This invention relates generally to electrode structures useful in applying electrical stimulating impulses to the body of a patient and more particular to an improved construction of such an electrode structure which provides improved flexibility without a corresponding sacrifice in the area of current distribution. As such, patient mobility is enhanced and so-called hot spots are avoided.
II. Description of the Prior Art
It has become well recognized that the application of pulse-type electrical stimulating signals to the body of a patient can produce generally therapeutic effects. For example, many forms of transcutaneous nerve stimulators are now available for use in the medical field. For example, in the Hagfors et al U.S. Pat. No. 3,911,930, there is described a body stimulating apparatus for ameliorating post-operative pain. The apparatus comprises a pulse generator which is adapted to be coupled to the body of the patient by way of surface electrodes.
The present invention pertains to the improved design of such surface electrodes. In the application of electrical stimulating current impulses to the body of a patient, it is desirable that the electrode structure be extremely flexible so as to conform to the skin surface of the patient, irrespective of the body motions which may take place at the electrode site. Furthermore, the goal of increased mobility must not be accompanied by an attendant inordinate increase in the current density at a localized site within the area covered by the electrode. Thus, the patient must be free to move without creating hot spots which might result in damage to the skin tissue or noxious pain.
Many forms of body electrodes are known in the art. For example, in the Kaufman U.S. Pat. No. 3,972,329, there is disclosed a disposable body electrode which is adapted to be adhesively attached to the body of the patient. It comprises a backing layer and a skin surface layer which sandwiches a generally rectangular metal electrode. The structure is designed to be adhesively secured to the patient's body. The conductive metal electrode portion of this structure comprises a rectangular sheet which is to be sufficiently flexible so as to conform to the contours of the body. Irrespective of the thickness of such metal electrode, as the surface area to be treated increases, there is a propensity for hot spots to develop should the electrode structure be bent or folded as by motion of the patient.
The invention of the Maurer U.S. Pat. No. 3,817,252 attempts to resolve this problem by utilizing a metal screen or mesh to achieve greater current distribution while maintaining a reasonable degree of flexibility to the electrode structure. A backing layer is provided having a terminal pin passing therethrough. The conductive screen is in electrical contact with the terminal pin and this screen is overlaid with a so-called diffuser screen. The skin interface pad overlaying the diffuser screen then completes the electrode structure.